The embodiment relates to an epoxy resin composition and a light emitting apparatus.
Recently, GaN white light emitting diodes (LED) have been extensively manufactured over the whole world. Methods for manufacturing the GaN white LED are mainly classified into two methods, one is a method using a single chip, in which a white LED is obtained by forming a phosphor layer on a blue LED or a UV LED, and the other is a method using a multi-chip, in which two or more LEDs are combined to obtain a white LED.
A representative method for manufacturing the white LED in the form of the multi-chip is to combine three R, G and B chips with each other. However, since operating voltage of each chip is not uniform, the output of each chip may vary depending on the surrounding temperature so that the color coordinate may be changed.
Due to the above problem, the multi-chip scheme is not suitable for implementing the white LED, but suitable for a special-purpose lighting that reproduces various colors by controlling the brightness of each LED using the circuit configuration.
For this reason, the binary system, which can be easily manufactured and obtained by combining a blue LED with a phosphor that is excited by the blue LED to generate yellow color, is representatively used to implement the white LED.
The binary system mainly employs a white LED, which uses the blue LED as an excitation light source and excites YAG (Yttrium Aluminum Garnet) phosphor using rare-earth 3-valent ion of Ce3+ as an activator, i.e., YAG:Ce phosphor using an excitation light emitted from the blue LED.
In addition, the white LED employs various packages according to applications, and representatively includes a surface mounting device (SMD) type ultra-miniaturized LED used in a backlight of a handheld terminal, and a vertical lamp type LED used for an electronic board, a solid display device or an image display.
Meanwhile, an index for analyzing the characteristics of white light includes a correlated color temperature (CCT) and a color rendering index (CRI).
The CCT indicates a temperature of an article when the article shines with emitting visible rays, it seems that a color of the article is identical to a color that a black body radiates at a temperature and it is assumed that the temperature of the black body is equal to that of the article. As the CCT becomes high, the light dazzles a human and becomes a bluish white.
Therefore, in spite of identical white lights, when the CCT is low, people feel warm, whereas when the CCT is high, people feel cold. Accordingly, it is possible to meet even the specification of a particular lighting requiring various color feelings by adjusting the CCT.
In a conventional white LED using the YAG:Ce phosphor, the CCT is fixed only to 6000K-8000K.
The CRI indicates a degree that the color of an article is changed when sun light or artificial light is irradiated onto the article. When the color of the article is identical to that under sun light, the CRI is defined as 100. In other words, the CRI is an index to show how the color of the article under the artificial lighting is close to that under sun light, and has a value of 0 to 100.
Accordingly, as the CRI approaches 100, i.e., white light, people can feel that the color of the article under the artificial lighting has no difference than that under sun light.
At present, an incandescent lamp has a CRI of 80 or more and a fluorescent lamp has a CRI of 75 or more, while a white LED using YAG:Ce phosphor has a CRI of approximately 70-75.
Accordingly, it is problematic that the white LED using the conventional YAG:Ce phosphor has the low CCT and low CRI.
In addition, since only the YAG:Ce phosphor is used, it is difficult to control the CCT, CRI and color temperature.
The LED using such a phosphor is disclosed in Korean Unexamined Patent Publication No. 10-2005-0098462.